小5聊纯javascript实现图片放大镜效果

Posted 2022-12-13 小5聊

实现图片放大镜效果，其实就是一个比例放大的效果

以下通过纯javascript方式对图片进行等比例放大，等比倍数和出界判断可自行实现

文章后面会附上全部代码

放大镜效果 

 

1、 放大镜组成

1）目标图片，一般是小图

2）鼠标移动上去的一个等比例小框框图

3）弹窗显示一个等比例的大图

2、实现分析

1）假如目标图片为宽度为500px，高度为200px，500:200的比例

2）那么定位遮罩就是，50:20

小方框遮罩和目标区域是50:500，10倍的关系

3）所以放大镜设置10倍比例就是，5000:2000

当然也可以设置动态比例参数，+-加减符号来调整

4）目标图片到浏览器顶部距离

关键点：targetObj.getBoundingClientRect().top，这个是到可视范围的浏览器顶部

特别注意：targetObj.offsetTop，这个值是指实际的距离，就是获取父元素的距离

5）获取class元素方法

querySelector和querySelectorAll

6）

3、布局设计

1）设置3张图片，统一设置class为targetImage

2）每张图片区域对应一个小方框遮罩，class为positionMask

当然这个遮罩也可以动态追加，此处不做实现

3）设置一个放大镜区域，样式class设置为enlargeArea

区域内就是具体的img标签，可以设置样式class为enlargeImage

<ul>
    <li>
        <img class="targetImage" src="" width="500" height="200" />
        <div class="postionMask"></div>
    </li>
    <li>
        <img class="targetImage" src="" width="500" height="200" />
        <div class="postionMask"></div>
    </li>
    <li>
        <img class="targetImage" src="" width="500" height="200" />
        <div class="postionMask"></div>
    </li>
</ul>

<div class="enlargeArea">
    <img class="enlargeImage" src="img/1200543.jpg" />
</div>

完整代码

<style>
    *  padding: 0; margin: 0; list-style: none; border: 0; 
    ul  width: 500px; height: 200px; overflow: hidden; margin-left: 100px; position: relative; 
        ul li  float: left; 
    .enlargeArea  box-shadow: 0 0 13px #ccc; height: 200px; width: 500px; overflow: hidden; position: fixed; top: 0; left: 0; background: #fff; border-radius: 10px; display: none; 
        .enlargeArea img  position: absolute; height: 2000px; width: 5000px; top: 0; left: 0; 
    .targetImage  position: relative 
    .postionMask  position: absolute; left: 0; top: 0; width: 50px; height: 20px; display: none; background-color: rgb(224, 117, 240, 0.6); 
</style>

<div style="width:100%;height:100px;"></div>
<ul>
    <li class="targetImageParent">
        <img class="targetImage" src="https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fpic1.win4000.com%2Fwallpaper%2F2%2F54699bf470c9a.jpg&refer=http%3A%2F%2Fpic1.win4000.com&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=auto?sec=1672062275&t=fa53ab442a8f11449e2c565745388654" width="500" height="200" />
        <div class="postionMask"></div>
    </li>
    <li class="targetImageParent">
        <img class="targetImage" src="https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fpic1.win4000.com%2Fwallpaper%2F2%2F57a2b93424164.jpg&refer=http%3A%2F%2Fpic1.win4000.com&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=auto?sec=1672062275&t=c270d62648a24edcd927f319b677d93a" width="500" height="200" />
        <div class="postionMask"></div>
    </li>
    <li class="targetImageParent">
        <img class="targetImage" src="https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fpic1.win4000.com%2Fwallpaper%2Fb%2F568e0e5a339f9.jpg&refer=http%3A%2F%2Fpic1.win4000.com&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=auto?sec=1672062275&t=62fcbf112e7c0b3fb9ebc197c725c2a2" width="500" height="200" />
        <div class="postionMask"></div>
    </li>
</ul>

<div class="enlargeArea">
    <img class="enlargeImage" src="https://gimg2.baidu.com/image_search/src=http%3A%2F%2Fpic1.win4000.com%2Fwallpaper%2F2%2F54699bf470c9a.jpg&refer=http%3A%2F%2Fpic1.win4000.com&app=2002&size=f9999,10000&q=a80&n=0&g=0n&fmt=auto?sec=1672062275&t=fa53ab442a8f11449e2c565745388654" />
</div>

<script type="text/javascript">

    // 获取目标图片有多少张
    var length = document.querySelectorAll('.targetImage').length;
    for (var i = 0; i < length; i++) 
        //给每张图片绑定事件
        bind(i);
    

    // 绑定事件
    function bind(i) 
        let targetImageParent = document.querySelectorAll(".targetImageParent")[i]; // 目标图片所在的父级对象
        let postionMask = document.querySelectorAll(".postionMask")[i];             // 小方框遮罩对象
        let enlargeArea = document.querySelector(".enlargeArea");                   // 放大镜区域
        let enlargeImage = document.querySelector(".enlargeImage");                 // 放大镜区域图片

        // 鼠标移开目标区域，隐藏放大镜弹窗和小方框遮罩
        targetImageParent.onmouseleave = function () 
            postionMask.style.display = "none";
            enlargeArea.style.display = "none";
        

        // 设置参数
        var starty = 0          // 鼠标进入目标区域的y轴坐标，也就是top值
        var startx = 0          // 鼠标进入目标区域的x轴坐标，也就是left值
        var maskStartTop = 0;   // 小方框遮罩左上角的x轴坐标值
        var maskStartLeft = 0;  // 小方框遮罩左上角的x轴坐标值

        // 鼠标进入目标区域，显示放大镜弹窗和小方框遮罩
        targetImageParent.onmouseenter = function (e) 
            starty = e.clientY;
            startx = e.clientX;

            var parent = this.parentElement;    // 这个需要注意，根据自己设定的固定区域来
            maskStartTop = parent.getBoundingClientRect().top;
            maskStartLeft = parent.getBoundingClientRect().left;
            postionMask.style.display = "block";

            // 放大镜图
            enlargeArea.style.display = "block";
            enlargeArea.style.top = maskStartTop - 100 + "px";
            enlargeArea.style.left = maskStartLeft + this.clientWidth + 20 + "px";

            // 获取src图片路径值
            enlargeImage.setAttribute('src', targetImageParent.getElementsByTagName('img')[0].getAttribute('src'));
        

        // 鼠标在目标区域移动
        targetImageParent.onmousemove = function (e) 

            let x = e.clientX - startx - postionMask.clientWidth / 2;
            let y = e.clientY - starty - postionMask.clientHeight / 2;

            var mY = e.clientY - maskStartTop - 5;
            //if (mY <= 0) mY = 0; // 可扩展移动到边界小方框遮罩不出借，此处暂不实现
            var mX = e.clientX - maskStartLeft - 25;
            //if (mX <= 0) mX = 0;

            // 小方框位置
            postionMask.style.top = mY + "px";
            postionMask.style.left = mX + 'px';

            // 放大镜图片对应显示，实际上就是等比定位
            enlargeImage.style.top = -(mY - 0) * 10 + 'px';
            enlargeImage.style.left = -(mX - 0) * 10 + 'px';
        
    
</script>